In a mobile communication network, a mobility management entity (Mobility Management Entity; MME) is used to perform operations such as saving mobility management context and user authentication on a terminal (User Equipment; UE) in a coverage area of a base station (E-UTRAN Node B; eNB). The eNB and the MME are connected through an S1 interface, and the eNBs are connected through an X2 interface. When the UE moves from a coverage area of one eNB to a coverage area of another eNB, the UE needs to be handed over from the first eNB to the second eNB.
In a conventional network, an eNB and a UE are connected through a wireless network, that is, a single-hop network. However, in a relay network, one or more relay nodes (Relay Node; RN) are added between an eNB and a UE, and are responsible for forwarding a radio signal sent by the eNB one time or multiple times to the UE. Taking a simple two-hop relay as an example, one eNB-UE radio link is divided into two radio links, namely, eNB-RN and RN-UE, thereby having the opportunity to replace one poor-quality link with two good-quality links, so as to achieve higher link capacity and a better coverage. The RN and a control base station (Donor E-UTRAN Node B; DeNB) that controls the RN are connected through a radio S1 interface and X2 interface. When the DeNB acts as an agent between the RN and an MME, the DeNB forwards an S1 message between the RN and the MME through the S1 interface, and when the DeNB acts as an agent between the RN and a base station adjacent to the RN, the DeNB forwards an X2 message between the RN and the base stations adjacent to the RN through an X2 interface.
In a convention network, when no X2 interface is available between two eNBs due to some reason, for example, when connection between the eNBs is interrupted due to external causes, if a UE is handed over from one eNB to another eNB, handover needs to be performed through an S1 interface connected to the MME, that is, a first eNB sends a handover request to a second eNB through the MME. However, in a relay network, when no X2 interface is available between an eNB and a DeNB, if a UE is handed over from the eNB to a RN that is controlled by the DeNB, as the MME cannot determine the DeNB corresponding to the RN, a handover request cannot be correctly sent, causing that the handover process cannot be performed normally.